Here are my two cents:

1) Down the road you would be wise to offer a builtup wing design.

2) sheet balsa or builtup stabs are entirely sufficient. Foam "airfoiled" stabs are not at all necessary, and will be more work than they are worth.

3) For scaling purposes, it would make good sense to plan to use as many wing "similarities" on all the planes as is possible. For instance, if you make builtup wings try to use the same ribs on several different planes or use the same foam cores.

Size doesn't make a difference at all to those of us who will fly these planes on electric power, but the virtual non-existence of viable glow engine options requires that you scale the planes around a set size, say the Norvel .061. A better option MAY be to enlarge the plane slightly to accept the OS/Enya/TT/Magnum .10 to .15 size engines, which would give us a workable throttle and a limitless supply of very good engines.

**edit** I just re-read the first post and realize you are already planning to use the OS .10 engine. I had my mind stuck on the Ace wings, so I thought of the smaller engines.

p.s. how about doing a model of the EU-1A? The original model was HUGE for its day (BARELY had enough power on a piped .60) and would work out quite well on a .15 to .20 I believe.